Fan is a common device for heat transfer engineering, and fans with a flow channel are mainly divided into two types, respectively: a centrifugal fan and an axial-flow fan. In the centrifugal fan, air enters from an axial direction of a fan wheel and the fan blows air out in a direction tangential to the rotation of the centrifugal fan. In the axial-flow fan, air enters and the fan blows air from the axial direction of the fan wheel. In the comparison of flow fields of the forgoing two types of fans, the flow field of the centrifugal fan has a greater static pressure and a smaller flow, and the flow field of the axial-flow fan has a smaller static pressure and a greater flow.
Different types of fans are provided to fit the installation requirements with different spaces. For example, the installation of the centrifugal fan is suitable for electronic devices with a small, narrow and flat space, and the installation of the axial-flow fan is suitable for computer chassis with sufficient installation space and having a larger quantity of generated heat than that of the mobile electronic devices.
With reference to FIGS. 1 and 2, a housing 10 of an automobile electronic device is suitable for installing an axial-feed-axial-exit axial-flow channel and applicable for the axial-flow fan. The rotating area of vanes 21 of the axial-flow fan 20 is equal to the cross-sectional area of the flow channel. If electronic devices are installed in this range, the airflow will be hindered, and thus electronic devices installed in the housing 10 are preferably installed at the positions of a fan hub 22 situated at the center of the axial-flow fan 20. However, the fan hub 22 of the axial-flow fan 20 generally comes with a small volume, and the space for installing the electronic devices in the housing 10 is limited. To optimize the operation of a flow channel, it is necessary to install a larger axial-flow fan 20 to obtain a greater area of the fan hub 22. For the axial-flow fan 20 of a regular size, the flow channel may be hindered by the electronic devices.